This invention relates to a bag maker-packaging machine of the type adapted to concurrently make bags and fill them with articles such as food items for packaging. In particular, this invention relates to a transverse sealer intended to be used in such a packaging machine for effecting thermal sealing of the bag-making material in the transverse direction.
So-called pillow-type packaging machines are a kind of bag maker-packaging machine capable of concurrently forming bags and filling these bags with articles to be packaged such as food items. An elongated web of bag-making material (herein referred to as "the film") is formed into a tubular shape by means of a device known as the former, and the film's mutually overlapping longitudinal side edges are sealed together first. While the tubularly formed film is pulled downward, it is thermally sealed in the transverse direction at the bottom by means of a transverse sealer comprising, for example, a pair of transverse seal jaws which may be disposed below a so-called filling cylinder used for filling the tubularly formed film with articles to be packaged. Because the formation of bags and the filling of the bags with articles to be packaged can be carried out concurrently and continuously, such bag maker-packaging machines are considered superior machines with high production efficiency.
Japanese Patent Publication Tokkai 63-30725, for example, disclosed a bag maker-packaging machine of a so-called rotary driven type characterized as moving its pair of transverse seal jaws linearly along the direction of motion of the film while their heat-applying surfaces are contacted to the film such that the transverse sealing can be effected over a sufficiently extended period of time.
A transverse sealer of this type does not give rise to any problem, as the seal jaws B are moved towards each other as shown by arrows in FIG. 8A to effect transverse thermal sealing, if the internal volume of the bag S is sufficiently large compared to the bulk of the articles w inside. Depending on the kind or condition of the articles W to be packaged, however, their volume sometimes becomes too large compared to the bag. This can happen, for example, when the water content of potatoes to be packaged is unusually high. In such a situation, as depicted in FIG. 8B, portions of the articles W to be packaged may be caught between the seal jaws B as they are closed, yielding defective products as a result. In order to prevent occurrences of this nature, it has been known to use the seal jaws as stripping means, as shown in FIG. 8C, holding the seal jaws B in a nearly-completely-closed condition (indicated by letter C) and to move them downward while the bag S remains closed so as to clear the area over which the bag S is to be transversely sealed. This operation is commonly known as "stripping."
Such stripping means C are not necessarily effective for the purpose of reducing empty spaces inside the bag because they are intended merely to strip the articles W downward where the transverse sealing is to take place.